Demographic response of tree juveniles to reduced-impact logging in a Costa Rican montane forest

We assessed diameter and height growth, and mortality in seedlings (individ uals greater than or equal to0.3, but <1.5 m tall) and saplings (individual s <greater than or equal to>1.5 m tall, but <10 cm DBH) of five common cano py tree species in an oak-bamboo forest in the Costs Rican highlands (2600- 2800 m elevation) 5 years after a controlled logging operation under two ha rvesting intensities (20 and 30% basal area removal of stems <greater than or equal to>10 cm DBH, respectively). The species were Quercus costaricensi s, Q. copeyensis, Drymis granadensis, Ocotea austinii, and Weinmania pinnat a. For seedlings, the overall 5-year mortality rate (exponential model) was significantly higher under the lightest harvest intensity while for saplin gs, no significant differences in mortality were detected among harvesting intensities. Also for all species combined, annual 5-year diameter and heig ht growth rates did not differ significantly among harvesting intensities f or seedlings, although saplings grew significantly better under the higher harvest intensity. Our results suggest that, as a whole, saplings of the st udy species were more responsive to overstory removal than seedlings. At th e species level, however, Quercus showed the largest significant difference s in growth rates across harvest intensities and also with respect to the o ther studied species in both size classes. Based on our findings, and given the high abundance of advance regeneration at the study site (especially f or Quercus), we propose that Costa Rican oak-bamboo forests show promising silvicultural potential for timber management under low-impact logging pres criptions. (C) 2001 Elsevier Science B.V. All rights reserved.